Rissveds crashed early on as Swiss hope Jolanda Neff and Anne Terpstra of the Netherlands swapped the lead before France's Pauline Ferrand-Prevot upped the ante.
Neff dropped back as the pace quickened with Swede Rissveds coming back superbly to challenge the stubborn Terpstra for the lead on the last lap.
The 25-year-old held her nerve brilliantly after her recent battle with depression to triumph from Terpstra and Ferrand-Prevot as a late puncture for Neff saw title rival Kate Courtney overtake her for seventh and crucial points ahead of their 2019 finale in Snowshoe.
Rissveds said: "So much emotion. Two years ago, I didn't want to be alive. It is possible and never give up like Pauline said last week. I was nervous before the start as I had to start on the front row and that is why I crashed in the first lap. The circle is complete. Three years ago I won this World Cup race and I won today."
In the men's race, Van der Poel started off strong after another short-track win on Friday with local hero Nino Schurter and Brazilian Henrique Avancini close behind.
Home hope Schurter was soon joined by another Swiss favourite in Mathias Flueckiger, however they could not shake off Van der Poel who put the hammer down in the closing laps with a searing pace that Schurter could not the match as the Dutchman won by 25 seconds.
It was his third win of 2019 and denied Schurter a record-equalling 33rd World Cup win, however the Swiss rider looks certain to win a seventh World Cup title as Van der Poel has opted not to race at the final USA stop to focus on the road cycling World Championship.
Van der Poel, 24, said: "This is maybe one of the most difficult ones to win especially because Nino is super motivated to win here in front of his home crowd. I knew it was going to be a tough one and I am very happy to make it work. I will stick to my main plan. I am very happy with my (mountain bike) season."
Schurter, 33, added: "He was definitely stronger and it is no shame to get second. I think my only chance to beat him was to go hard from the beginning. It is not nice if someone is missing in a tight battle, but I am also looking forward to winning another overall."
1. Jenny Rissveds SWE 1:21.09
2. Anne Terpstra NED +0.25
3. Pauline Ferrand-Prevot FRA +1.19
4. Sina Frei SUI +2.03
5. Catharine Pendrel CAN +2.12
Women's UCI MTB World Cup XCO standings:
1. Jolanda Neff SUI 1625 points
2. Kate Courtney USA 1552
3. Pauline Ferrand-Prevot FRA 1225
4. Anne Terpstra NED 1210
5. Rebecca McConnell AUS 992
Men's UCI MTB World Cup XCO race at Lenzerheide:
1. Mathieu van der Poel NED 1:17.50
2. Nino Schurter SUI +0.25
3. Mathias Flueckiger SUI +1.13
4. Victor Koretzky FRA +1.44
5. Gerhard Kerschbaumer ITA +1.44
Men's UCI MTB World Cup XCO standings:
1. Nino Schurter SUI 1670 points
2. Mathieu van der Poel NED 1649
3. Henrique Avancini BRA 1360
4. Mathias Flueckiger SUI 1348
5. Gerhard Kerschbaumer ITA 970